The cooling system of numerous types of automotive engines has fluid flow conduit structure in which there are a plurality of flow passages. This type of structure is sometimes referred to as a fluid flow by-pass cooling system. A conventional by-pass valve structure includes a hollow closure member, open at each end, which is slidably movable within an opening within the conduit structure. The closure member is capable of directing fluid flow directly from one flow passage to another flow passage, and is axially movable to provide communication between two flow passages while closing communication between two of the flow passages. The size of the opening within which the hollow closure member is movable is predetermined by the engine manufacturer and is smaller than the size of an opening in the valve seat member within which an actuator portion of the valve device is positioned. The actuator portion of the valve device occupies a significant area, and thus the area for fluid flow through the opening is reduced. In order to provide maximum area for fluid flow through the valve seat member it is customary to have the largest opening possible through the valve seat member. This opening is greater than the opening through the closure member. It has been customary to provide an inclined portion at the end of the hollow closure member which engages the valve seat member so that the opening through the valve seat member is a maximum and the opening into the closure member is a maximum, even though the opening through the closure member is smaller.
However, it has been found that an inclined flange at the entrance end of the hollow closure member in the conventional by-pass valve device is objectionable due to the fact that pressure of the fluid engaging the inclined flange may be sufficient to move the closure member from the valve seat. Such movement of the closure member as a result of pressure is objectionable due to the fact that operation of the valve device should be responsive only to temperature and should not be affected by fluid pressures.
Therefore, it is an object of this invention to provide a thermally responsive by-pass valve device which includes means by which a maximum fluid flow area can be maintained through an opening in a valve seat member within which an actuator member is disposed, while maintaining the valve device as one which is not affected by fluid pressures.
It is another object of this invention to provide such a by-pass valve device which readily replaces a conventional by-pass type of valve device.
It is another object of this invention to provide such a thermally responsive by-pass valve device which can be produced at substantially the same costs as a conventional type of thermally responsive by-pass valve device.
U.S. Pat. Nos. 2,919,860 and 3,129,885 disclose structure of the same general type as that of this invention; however, in the devices of each of these patents, elements are not arranged to provide maximum fluid flow through a valve seat member within which a thermally responsive actuator member is positioned.